IIRC the hole tolerances are rather loose on the valve cover.
Try loosening all of the screws and seeing if the cover will shift over a bit and remove the interference.
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ